Dental materials using thermoset polymers

ABSTRACT

Provided herein are crosslinked polymers useful in orthodontic appliances and light polymerizable liquid compositions and formulations useful for making crosslinked polymers. Also provided are methods of making an orthodontic appliance comprising a cross-linked polymer formed by a direct fabrication technique.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/189,380, filed Jul. 7, 2015 which is hereby incorporated by referencein its entirety.

BACKGROUND

Orthodontic procedures typically involve repositioning a patient's teethto a desired arrangement in order to correct malocclusions and/orimprove aesthetics. To achieve these objectives, orthodontic appliancessuch as braces, retainers, shell aligners, and the like can be appliedto the patient's teeth by an orthodontic practitioner. The appliance isconfigured to exert force on one or more teeth in order to effectdesired tooth movements. The application of force can be periodicallyadjusted by the practitioner (e.g., by altering the appliance or usingdifferent types of appliances) in order to incrementally reposition theteeth to a desired arrangement.

FIG. 1A illustrates an exemplary orthodontic appliance 106 and jaw 104including a patient's teeth, as presented in US Patent ApplicationPublication 2015/0004553, the disclosure of which is incorporated hereinby reference in its entirety. FIG. 1B illustrates orthodontic appliancecross-section 112 as taken along line 1B-1B of FIG. 1A, while FIG. 10illustrates orthodontic appliance cross-section 118 as taken along line1C-1C of FIG. 1A. The orthodontic appliance 106 may be designed to fitover a number of teeth present in an upper or lower jaw. As illustrated,the orthodontic appliance has a U-shaped cross-section to form one ormore cavities for placement of a patient's teeth therein.

BRIEF SUMMARY

Provided herein are crosslinked polymers useful in orthodonticappliances and light polymerizable liquid compositions and formulationsuseful for making crosslinked polymers. Also provided are methods ofmaking an orthodontic appliance comprising a cross-linked polymer formedby a direct fabrication technique. Direct fabrication can providevarious advantages compared to other manufacturing approaches. Forinstance, in contrast to indirect fabrication, direct fabricationpermits production of an appliance without utilizing any molds ortemplates for shaping the appliance, thus reducing the number ofmanufacturing steps involved and improving the resolution and accuracyof the final appliance geometry. Additionally, direct fabricationpermits precise control over the three-dimensional geometry of theappliance, such as the appliance thickness.

In many embodiments, direct fabrication is used to produce appliancegeometries that would be difficult to create using alternativemanufacturing techniques, such as appliances with very small or finefeatures, complex geometric shapes, undercuts, interproximal structures,shells with variable thicknesses, or internal structures (e.g., forimproving strength with reduced weight and material usage). Forinstance, in many embodiments, the direct fabrication approaches hereinpermit fabrication of an orthodontic appliance with feature sizes ofless than or equal to about 5 μm, or within a range from about 5 μm toabout 50 μm, or within a range from about 20 μm to about 50 μm. Thedirect fabrication techniques described herein can be used to produceappliances with substantially isotropic material properties, e.g.,substantially the same or similar strengths along all directions. Insome embodiments, the direct fabrication approaches herein permitproduction of an orthodontic appliance with a strength that varies by nomore than about 25%, about 20%, about 15%, about 10%, about 5%, about1%, or about 0.5% along all directions. Additionally, the directfabrication approaches herein can be used to produce orthodonticappliances at a faster speed compared to other manufacturing techniques.In some embodiments, the direct fabrication approaches herein allow forproduction of an orthodontic appliance in a time interval less than orequal to about 1 hour, about 30 minutes, about 25 minutes, about 20minutes, about 15 minutes, about 10 minutes, about 5 minutes, about 4minutes, about 3 minutes, about 2 minutes, about 1 minutes, or about 30seconds. Such manufacturing speeds allow for rapid “chair-side”production of customized appliances, e.g., during a routine appointmentor checkup.

Orthodontic appliances using the materials and method described hereininclude, but are not limited to, braces, retainers and shell aligners.The appliances can have different materials/formulation, shapes, and/orsize/thickness from one area to another area with different force designin mind using multiple materials formulations. In embodiments, amulti-material direct fabrication method can involve forming an objectfrom multiple materials in a plurality of sequential manufacturingsteps. For instance, a first portion of the object (e.g., an interiorlayer) can be formed from a first material in accordance with any of thedirect fabrication methods described herein, then a second portion ofthe object (e.g., an exterior layer) can be formed from a secondmaterial in accordance with methods herein, and so on, until theentirety of the object has been formed. In further embodiments, amulti-tip extrusion apparatus can be used to selectively dispensemultiple types of materials from distinct material supply sources inorder to fabricate an object from a plurality of different materials.Such methods are described in U.S. Pat. No. 6,749,414, the disclosure ofwhich is incorporated herein by reference in its entirety.

In embodiments, the orthodontic appliance is a tooth position adjustmentdental appliance having cavities shaped to receive and resilientlyreposition teeth from a first arrangement to a second arrangement. Forexample, a dental appliance can include a shell formed of cross-linkedpolymer materials and having a number of cavities to receive one or moreteeth. In some embodiments, the shell is formed of thermoset polymermaterials. In one or more apparatus embodiments, the dental appliance isan aligner (e.g., shell) having a number of cavities to receive one ormore teeth. In embodiments, the aligner is one of a series of alignerscorresponding to intermediate steps of an orthodontic treatment wherethe number of cavities are arranged to reposition the one or more teethfrom a first configuration to a successive configuration, and thealigner is fabricated from material that is irreversibly cured toirreversibly link molecules into a rigid three dimensional structure. Adental appliance (e.g., a dental positioning appliance such as analigner, a tray for delivery of chemicals in proximity to the teeth orgums, etc.) can include a number of cavities for receiving one or morecorresponding teeth. In various embodiments, the cavities can correspondto one, or multiple, teeth, implants, and/or other features of apatient's jaw.

In embodiments, the crosslinked polymer comprises crosslinks formed bycovalent interactions. In further embodiments, the crosslinked polymeralso comprises crosslinks formed by non-covalent interactions. Inembodiments, the crosslinked polymer is a thermoset polymer. Inembodiments, the crosslinked polymer forms a crosslinked network.

In embodiments, the crosslinked polymer is selected from the groupconsisting of polyurethanes, (meth)acrylates, epoxies and copolymersthereof. As used herein, (meth)acrylate is shorthand for acrylate and/ormethacrylate and a polyurethane polymer or oligomer includes at leastone urethane linkage, also known as a carbamate linkage. In a furtherembodiment, the crosslinked polymer is an epoxy acrylate, a modifiedepoxy acrylate, epoxy methacrylate or a urethane acrylate. Inembodiments, the crosslinked polymer is a copolymer. In embodiments, thecrosslinked polymer is biocompatible. In different embodiments, thecrosslinked polymer is transparent, translucent or opaque. Transparentcrosslinked polymers may be clear or tinted to achieve various colors.In some embodiments the crosslinked polymer is characterized by atransmittance equal to or greater than 80% for light having a wavelengthin the visible region.

In an aspect the crosslinked polymer has a tensile strength at yield ofgreater than 4000 psi (27.6 MPa) or from 20 MPa to 55 MPa. Inembodiments, the tensile modulus is greater than 150,000 psi (1034 MPa)or from 800 MPa to 2000 MPa. In further embodiments, the elongation atyield is greater than 4%, greater than 4% and less than or equal to 25%,or greater than 4% and less than or equal to 10%. In additionalembodiments, the elongation at break is greater than 30%, greater than40%,greater than 40% and less than or equal to 250% or greater than 40%and less than or equal to 80%. Tensile and elongation properties may bemeasured per ASTM D 638-14. The water absorption may be less than onepercent. In an embodiment, the glass transition temperature is greaterthan 90° C. and the deflection temperature is greater than 90° C. Infurther embodiments, the glass transition temperature is from 38° C. to90° C. or from 40° C. to less than 90° C. In embodiments, the amount ofstress relaxation at 37° C. at 24 hours and 100% relative humidity issuch that the remaining load is greater than 80% of the initial load,greater than 50% of the initial load, greater than 25% of the initialload or greater than 10% of the initial load. In embodiments, the amountof stress relaxation at 37° C. at 14 days and 100% relative humidity issuch that the remaining load is greater than 50% of the initial load,greater than 25% of the initial load or greater than 10% of the initialload. In further embodiments, the stress relaxation at 37° C. at 24hours and 100% relative humidity is such that the remaining load isgreater than 80% of the initial load (stress relaxation less than 20%)and at 14 days at 100% relative humidity the remaining load is greaterthan 50% of the initial load (stress relaxation less than 50%). Inembodiments, the dimensional stability of the crosslinked polymer issuch an orthodontic appliance including the crosslinked polymer meetsdimensional specifications when placed in an oral environment, therebymaintaining fit of the appliance for the patient. In embodiments, thecrosslinked polymer is used to form a shell of a tooth positioningaligner; the shell may span the entire arch.

In some aspects, a crosslinked polymer is provided having a tensilemodulus, a tensile strength at yield, an elongation at yield and anelongation at break as described above. In some embodiments, acrosslinked polymer is provided having a tensile modulus from 800 MPa to2000 MPa, a tensile strength at yield of 20 MPa to 55 MPa, an elongationat yield greater than 4% and an elongation at break greater than 30%.

In an aspect, the crosslinked polymers provided herein are formed bypolymerization of a light polymerizable liquid composition orformulation comprising at least two polymerizable components. In afurther aspect, the light polymerizable liquid composition comprisesthree polymerizable components. In embodiments, the light polymerizableliquid composition further comprises a photoinitiator. In furtherembodiments, the light polymerizable liquid composition furthercomprises a radical stabilizer, an inhibitor, a filler or a combinationthereof. Suitable fillers include soluble filler and inorganic fillers.

In an aspect, a polymerizable component comprises at least onepolymerizable group. Polymerizable groups include, but are not limitedto, vinyl groups, ally groups, acrylate groups, methacrylate groups,acrylamide groups, epoxy groups and oxetanyl groups. As used herein,when a polymerizable component is stated to be a monomer or oligomer, aplurality of monomer or oligomer molecules of the specified type isintended to be included. A polymerizable component, such as a monomer oroligomer, may be characterized by the polymerizable groups of themonomer, by other functional groups of the monomer, or a combinationthereof. As used herein, vinyl monomers or oligomers are monomers oroligomers including a vinyl group and include, but are not limited to,monomers or oligomers having acrylate, methacrylate or acrylamidegroups. In some embodiments, vinyl monomers or oligomers not includingmeth (acrylate) groups are characterized as non-(meth) acrylate monomersor oligomers.

In embodiments, the formulation comprises at least one urethane (meth)acrylate prepolymer, monomer or oligomer. For example, the urethane(meth)acrylate prepolymer, monomer or oligomer is selected from thegroup consisting of Exothane 108, Exothane 10, isophorone urethanedimethacrylate (IPDI-UDMA), CN991, CN9782, CN3211, CN9782, CN9009,PU3201 NT and combinations thereof. In some embodiments, the urethane(meth)acrylate prepolymer, monomer or oligomer is an aliphatic urethanedimethacrylate. In other embodiments, the (meth)acrylate prepolymer,monomer or oligomer is an aliphatic urethane diacrylate. In furtherembodiments, the urethane (meth) acrylate prepolymer or oligomer has aviscosity of from 100,000 centipoise (cP) to 1,000,000 cP as measured at25° C., from 10,000 cP to 50,000 cP as measured at 60° C., from 10,000centipoise (cP) to 50,000 cP as measured at 25° C. or from 500 cP to50,000 cP as measured at 60° C.

In additional embodiments, the formulation further comprises at leastone vinyl monomer. For example, suitable vinyl monomers are selectedfrom the group consisting of SR833S, SR368D, β-carboxyethylacrylate(CEA), and 1-vinyl-2-pyrrolidinone (NVP), M1130 (trimethyl cyclohexylacrylate TMCHA), M151 (tetrahydrofurfuryl methacrylate, THFMA),isobornyl acrylate (IBOA), isobornyl methacrylate (IBOMA) andcombinations thereof. In a further embodiment, the vinyl monomer is1,3,5-Triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (TATATO). TATATOmay be used in combination with a thiol monomer. Exothane 108, Exothane10, IPDI-UDMA or UDMA-IPDI (Esstech, Inc., identified as IsophoroneUrethane dimethacrylate) are available from Esstech, Inc. (Essington,Pa.). CN991, CN9782 and CN3211, SR833S (also identified as 833 S,Tricyclodecane dimethanol diacrylate), SR368D (also identified as SR 368D, Tris (2-hydroxy ethyl) isocyanurate triacrylate), CN9782, CN9009 andCN3211 are available from Sartomer (Exton, Pa.). PU3201NT, M1130, M151,IBOA, and IBOMA are available from Miwon (Anyang, South Korea). See alsoTable 3.

In embodiments, the vinyl monomer is a (meth)acrylate monomer which doesnot include a urethane linkage. Exemplary (meth)acrylate monomers whichdo not include a urethane linkage have a viscosity from 1 to 400 cP at25° C. In embodiments, the number of (meth)acrylate functional groups isfrom 1 to 3.

In additional embodiments, the vinyl monomer does not include a urethanelinkage or (meth)acrylate functional groups. Exemplary vinyl monomerswhich do not include a urethane linkage or (meth)acrylate functionalgroups include vinyl functional groups or allyl functional groups. Inembodiments, such vinyl monomers have a viscosity from 1 to 200 cP at25° C. In embodiment, the number of vinyl or allyl functional groups isfrom 1 to 3.

In a further aspect the formulation includes two polymerizablecomponents. In some embodiments, the crosslinked polymer comprises afirst repeating unit derived from a urethane (meth)acrylate oligomer anda second repeating unit derived from a vinyl or thiol monomer wherein atleast one of the urethane (meth)acrylate oligomer, the vinyl monomer andthe thiol monomer comprises at least two polymerizable groups. In anembodiment, amount of the first component is from 15-40 wt % and theamount of the second component is from 15 to 75 wt %.

In some embodiments, the crosslinked polymer comprises a first repeatingunit derived from a urethane (meth)acrylate oligomer and a secondrepeating unit derived from a vinyl or thiol monomer wherein at leastone of the urethane (meth)acrylate oligomer, the vinyl monomer and thethiol monomer comprises at least two polymerizable groups. The urethane(meth)acrylate oligomer and the vinyl or thiol monomer are as describedherein. In some embodiments, the amount of the first repeating unit isfrom 25 to 50 wt % and the amount of the second repeating unit is from50 to 75 wt %, with the total amount of the first repeating unit and thesecond repeating unit being greater than or equal to 70 wt %.

In an aspect, the formulations contain three polymerizable components.The first component may be regarded as a base component. In embodiments,the first component is a monomer or oligomer. In embodiments the firstcomponent is selected from the group of consisting of acrylates,methacrylates, vinyl esters, polyurethane with acrylate end groups andpolyurethane with epoxy end groups. As examples, the first componentcomprises a functional group selected from polyurethane, acrylate,methacrylate, vinyl ester, epoxy, oxetanyl and combinations thereof. Infurther embodiments, the first component comprises a functional groupselected from polyurethane, acrylate, epoxy, and combinations thereof.Some biocompatible monomers include tetraethylene glycol diacrylate(E4-A), diisopropyl acrylamide (DPA), diisobutylacrylamide (DBA),2-(2-ethoxy-ethoxy) ethyl acrylate, trimethylolpropanetriacrylate (TTA)and urethanedimethacrylate (UDMA).

In embodiments, the first component is a urethane (meth)acrylate monomeror oligomer. In embodiments the urethane portion of the monomer oroligomer may be aliphatic or aromatic. In embodiments, the number of(meth)acrylate groups in the monomer is 1, 2 or 3. In furtherembodiments, the urethane (meth)acrylate monomer or oligomer is selectedfrom the group consisting of a dimethacrylate urethane oligomer, anisophorone urethane dimethacrylate oligomer, a urethane diacrylateoligomer and a urethane triacrylate oligomer. As examples, suitableurethane (meth)acrylate monomers and oligomers are selected from thegroup consisting of Exothane 108, Exothane 10, IPDI-UDMA, CN991, CN9782,CN9782, CN3211, CN9009, PU3201NT and combinations thereof. Inembodiments, the first component is selected from the group consistingof Exothane 108, Exothane 10, IPDI-UDMA or UDMA-IPDI (identified asIsophorone Urethane dimethacrylate), CN991, CN9782, CN9009, PU3201NT andCN3211. In some embodiments, the viscosity of the first component isgreater than the viscosity of the other monomer or oligomer componentsin the formulation.

In some embodiments, the second component may be regarded as a reactivediluent. In embodiments, the second component comprises a functionalgroup selected from polyurethane, acrylate, methacrylate, vinyl ester,epoxy, and combinations thereof. As examples, the second component is anacrylate, epoxy or urethane based diluent. In some embodiments, thesecond component is a vinyl monomer or a thiol monomer. As examples, thesecond component is selected from the group consisting of diacrylatemonomers, triacrylate monomers, acyclic diacrylate monomers, cyclicdiacrylate monomers, methacrylate monomers, vinyl ester monomers,polyurethane monomers with acrylate end groups and polyurethane monomerswith epoxy end groups. In further embodiments, the third component is avinyl monomer which does not include a urethane group. Such vinylmonomers include (meth)acrylate monomers and vinyl monomers which do notinclude (meth)acrylate groups. As examples, the second component isselected from 1-vinyl-2-pyrrolidinone (NVP), CEAβ-carboxyethylacrylate), trimethyl cyclohexyl acrylate (M1130),isobornyl acrylate (IBOA), Isobornyl methacrylate (IBOMA),tetrahydrofurfuryl methacrylate (M151) and one of PETMP and TATATO (seeTable 4). In some embodiments, the viscosity of the reactive diluentcomponent(s) (e.g. the second component) is less than the viscosity ofother monomer or oligomer components in the formulation (e.g. the firstand the third components).

In some embodiments, the third component may be regarded as a modifier.In embodiments, the third component is a vinyl monomer or a thiolmonomer. In further embodiments, the third component is a urethane(meth)acrylate monomer or oligomer. In embodiments the urethane portionof the monomer or oligomer may be aliphatic or aromatic. In anembodiment, the number of (meth)acrylate groups in the monomer is 1 or2. In further embodiments, the third component is a vinyl monomer whichdoes not include a urethane group. Such monomers include (meth)acrylatemonomers. In an embodiment in which the formulation includes a thiol-enesystem, the second component is one of a vinyl monomer or a thiol andthe third component is the other of a vinyl monomer or a thiol. Forexample, when the second component is one of PETMP and TATATO, the thirdcomponent is the other of PETMP and TATATO. As examples, the thirdcomponent is selected from SR833S, SR368D, CN9782, CN3211,tris(2-hydroxy ethyl)isocyanurate triacrylate (M370), tricyclodecanedimethanol diacrylate (TCDDA), PE210, tripropylene glycol diacrylate(TPGDA), PU340, ME2110 and NVP (see Tables 3 and 4). In someembodiments, the viscosity of the modifier component(s) (e.g. the secondcomponent) is less than the viscosity of the first component in theformulation.

In embodiments of a formulation including three polymerizablecomponents, the amount of the first repeating unit is from 15-40 wt %,the amount of the second repeating unit is from 15 to 75 wt % and theamount of the third repeating unit is from 2 to 60 wt %. In a furtherembodiment, the total amount of the first repeating unit, the secondrepeating unit and the third repeating unit is greater than or equal to70 wt %. 80 wt % or 90 wt %. In further embodiments the amount of thefirst repeating unit is from 20-35 wt %, the amount of the secondrepeating unit is from 20 to 70 wt % and the amount of the thirdrepeating unit is from 2 to 45 wt %, 2 to 20 wt %, 15 to 45 wt % or 20to 40 wt %. In yet a further embodiment, the total amount of the firstrepeating unit, the second repeating unit and the third repeating unitbeing greater than or equal to 70 wt %. 80 wt % or 90 wt %.

An exemplary formulation comprising three polymerizable componentsincludes a urethane (meth)acrylate monomer or oligomer and two vinylmonomers, each of which does not include a urethane group. In someembodiments, one of the vinyl monomers is an acrylate monomer. Anexemplary formulation includes a urethane (meth) acrylate prepolymer, anon-urethane acrylate monomer and a non-acrylate vinyl monomer. Anotherexemplary formulation includes a urethane (meth)acrylate prepolymer andtwo non-urethane acrylate monomers. Another exemplary formulation withthree polymerizable components includes two different urethane(methacrylate) monomers or oligomers and a vinyl monomer which does notinclude a urethane group. Another exemplary formulation with threepolymerizable components includes two different urethane (methacrylate)monomers or oligomers and a vinyl monomer which does not include aurethane group or an acrylate group. A further exemplary formulationincludes a urethane (methacrylate) monomer or oligomer, a thiol monomerand a vinyl monomer, wherein neither the thiol monomer nor the vinylmonomer includes a urethane group.

In an aspect, the crosslinked polymer comprises a first repeating unitderived from a first urethane (meth) acrylate oligomer, a secondrepeating unit derived from a first vinyl or thiol monomer not includinga urethane linkage and a third repeating unit derived from a secondurethane (meth) acrylate oligomer or a second vinyl or thiol monomer notincluding a urethane linkage, wherein at least one of the urethane(meth) acrylate oligomer(s) and the vinyl or thiol monomer(s) comprisesat least two polymerizable groups. In some embodiments, the amount ofthe first repeating unit is from 15-40 wt %, the amount of the secondrepeating unit is from 15 to 75 wt % and the amount of the thirdrepeating unit is from 2-60 wt %, with the total amount of the firstrepeating unit, the second repeating unit and the third repeating unitbeing greater than or equal to 70 wt %.

Photoinitiators suitable for use in the polymerizable liquidcompositions of the invention include, but are not limited tophotoinitiators activated by UV or visible light. In embodiments, thephotoinitiator is activated by long-wavelength UV light or UVA(wavelength approximately 320 to 400 nm). Photo-initiators activated bylong wavelength UV light include, but are not limited to, 2, 4,6-trimethylbenzoylphenyl phosphinate (Irgacure®TPO-L), acylgermanes, abimolecular system of camphorquinone (CQ) and N, N-dimethylaminobenzoicacid ethyl ester (DMAB), bisacylphosphine oxides (Irgacure 819) andhydroxyalkylphenones (Irgacure 2959) and 1,5-diphenyl-1,4-diyn-3-one(Diinone). Camphorquinone (CQ), N, N-dimethylaminobenzoic acid ethylester (DMAB) bisacylphosphine oxides (Irgacure 819),hydroxyalkylphenones (Irgacure 2959) and 1,5-diphenyl-1,4-diyn-3-one(Diinone) are biocompatible. In some embodiments, the formulationincludes from 0.1 wt % to 3 wt % photoinitiator. In further embodiments,the formulation does not include a second type of initiator other than aphotoinitiator.

In an aspect, the viscosity of the polymerizable liquid composition issuitable for use with a direct or additive manufacturing process. Inembodiments, the viscosity of the polymerizable liquid composition isless than 4000 cP, less than 2000 cP, less than 700 cP, from greaterthan or equal to 500 cP to less than 4000 cP, from greater than or equalto 500 cP to less than 2000 cP, from greater than or equal to 200 cP toless than 4000 cP or from greater than or equal to 200 cP to less than2000 cP. The viscosity may be measured at the process temperature. Theprocess temperature can be adjustable from room temperature (˜25° C.) tohigher temperature such as 80° C. or higher in order to achieve thedesired process viscosity and speed.

In an aspect, the crosslinked polymer is formed via a direct or additivemanufacturing process. Direct or additive manufacturing processes mayalso be termed 3D printing. Suitable manufacturing processes include,but are not limited to, stereolithography (SLA), micro-stereolithography(μSLA), DLP projection, 2PP (two photon polymerization), continuousliquid interface production and material jetting. In embodiments, thedirect fabrication methods described herein build up the object geometryin a layer-by-layer fashion, with successive layers being formed indiscrete build steps. In particular embodiments, an at least partiallycrosslinked polymer is formed by sequential formation of polymer layerson a surface of a build plate, wherein at least that surface of thebuild plate is immersed in a vat or reservoir of a formulationcomprising polymerizable components. In embodiments the polymer isformed by exposure of the formulation to light of suitable wavelengthsand intensity to activate the photoinitiator in the formulation andcause photopolymerization of polymerizable components in theformulation. The build plate is typically moved with respect to the vator reservoir (e.g., along the vertical or Z-direction) during theirradiation phase. In some embodiments, the build plate is moved awayfrom the free surface of the formulation (e.g. moved deeper into thevat) as irradiation progresses. In other embodiments, the build plate ismoved away from the base of the vat as irradiation progresses.

Alternatively or in combination, direct fabrication methods that allowfor continuous or nearly continuous build-up of an object geometry canbe used, referred to herein as “continuous direct fabrication.” Varioustypes of continuous direct fabrication methods can be used. As anexample, in embodiments, the crosslinked polymers herein are fabricatedusing “continuous liquid interphase printing,” in which an object iscontinuously built up from a reservoir of photopolymerizable resin byforming a gradient of partially cured resin between the building surfaceof the object and a polymerization-inhibited “dead zone.” In manyembodiments, a semi-permeable membrane is used to control transport of aphotopolymerization inhibitor (e.g., oxygen) into the dead zone in orderto form the polymerization gradient. In an embodiment, the oxygenconcentration is greater near the base of the reservoir than at thesurface of the build plate and the build plate is moved away from thebase of the reservoir during irradiation. Continuous liquid interphaseprinting can achieve fabrication speeds about 25 times to about 100times faster than other direct fabrication methods, and speeds about1000 times faster can be achieved with the incorporation of coolingsystems. Continuous liquid interphase printing is described in U.S.Patent Publication Nos. 2015/0097315, 2015/0097316, and 2015/0102532,the disclosures of each of which are incorporated herein by reference intheir entirety.

The crosslinked polymer may undergo post processing following directfabrication. In some embodiments, the crosslinked polymer may besubjected to chemical extraction to remove small molecule contents (e.g.uncured or unpolymerized monomers and/or oligomers, photoinitiators andother components). In embodiments, a single solution or multiplesolutions are used for chemical extraction. As an example, multiplesolutions used for extraction differ in the nature and/or concentrationof the solution components. The processes can also include a dual curingsystem in order to achieve a high level of curing of the final parts. Inembodiments, an initial level of crosslinking is achieved during thedeposition of the part and a further crosslinking is achieved byadditional exposure to light (“post-curing”). In a further embodiment,the first step is to be achieved with slower reaction with mixingcatalysts or fast reaction by light source: the second step will becompleted with a gamma source e-beam, or heat for a continuous process.In embodiments, the light source provides UV light.

In some embodiments, methods of making an orthodontic appliancecomprising a cross-linked polymer comprise the steps of:

providing a light polymerizable liquid composition comprising:

-   -   a first polymerizable component, wherein the first polymerizable        component is selected from the group consisting of an acrylate        monomer or oligomer, a methacrylate monomer or oligomer, a vinyl        ester monomer or oligomer, an acrylamide monomer or oligomer; a        thiol monomer or oligomer, urethane monomer or oligomer, an        epoxy monomer or oligomer and a oxetane monomer or oligomer;    -   a second polymerizable component, wherein the second        polymerizable component is a vinyl monomer or oligomer, thiol        monomer or oligomer, a urethane monomer or oligomer and an epoxy        monomer or oligomer; and    -   a photoinitiator;    -   wherein at least one of the first and second polymerizable        components comprises at least two polymerizable groups; and

fabricating the cross-linked polymer by a direct fabrication technique.

The liquid polymerizable liquid compositions or formulations are asdescribed elsewhere herein. Similarly, suitable fabrication techniquesare described herein.

The various embodiments of the orthodontic appliances presented hereincan be fabricated in a wide variety of ways. In some embodiments, theorthodontic appliances herein (or portions thereof) can be producedusing direct fabrication, such as additive manufacturing techniques(also referred to herein as “3D printing”) or subtractive manufacturingtechniques (e.g., milling). In some embodiments, direct fabricationinvolves forming an object (e.g., an orthodontic appliance or a portionthereof) without using a physical template (e.g., mold, mask etc.) todefine the object geometry. Additive manufacturing techniques can becategorized as follows: (1) vat photopolymerization (e.g.,stereolithography), in which an object is constructed layer by layerfrom a vat of liquid photopolymer resin; (2) material jetting, in whichmaterial is jetted onto a build platform using either a continuous ordrop on demand (DOD) approach; (3) binder jetting, in which alternatinglayers of a build material (e.g., a powder-based material) and a bindingmaterial (e.g., a liquid binder) are deposited by a print head; (4)fused deposition modeling (FDM), in which material is drawn though anozzle, heated, and deposited layer by layer; (5) powder bed fusion,including but not limited to direct metal laser sintering (DMLS),electron beam melting (EBM), selective heat sintering (SHS), selectivelaser melting (SLM), and selective laser sintering (SLS); (6) sheetlamination, including but not limited to laminated object manufacturing(LOM) and ultrasonic additive manufacturing (UAM); and (7) directedenergy deposition, including but not limited to laser engineering netshaping, directed light fabrication, direct metal deposition, and 3Dlaser cladding. For example, stereolithography can be used to directlyfabricate one or more of the appliances herein. In some embodiments,stereolithography involves selective polymerization of a photosensitiveresin (e.g., a photopolymer) according to a desired cross-sectionalshape using light (e.g., ultraviolet light). The object geometry can bebuilt up in a layer-by-layer fashion by sequentially polymerizing aplurality of object cross-sections. As another example, the appliancesherein can be directly fabricated using selective laser sintering. Insome embodiments, selective laser sintering involves using a laser beamto selectively melt and fuse a layer of powdered material according to adesired cross-sectional shape in order to build up the object geometry.As yet another example, the appliances herein can be directly fabricatedby fused deposition modeling. In some embodiments, fused depositionmodeling involves melting and selectively depositing a thin filament ofthermoplastic polymer in a layer-by-layer manner in order to form anobject. In yet another example, material jetting can be used to directlyfabricate the appliances herein. In some embodiments, material jettinginvolves jetting or extruding one or more materials onto a build surfacein order to form successive layers of the object geometry.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates an exemplary dental appliance 106 and jaw 104including a patient's teeth.

FIG. 1B illustrates dental appliance cross-section 112 as taken alongline 1B-1B of FIG. 1A, while FIG. 10 illustrates dental appliancecross-section 118 as taken along line 1C-1C of FIG. 1A.

DETAILED DESCRIPTION

As used herein, the term “polymer” refers to a molecule composed ofrepeating structural units connected by covalent chemical bonds oftencharacterized by a substantial number of repeating units (e.g., equal toor greater than 10 repeating units and often equal to or greater than 50repeating units and often equal to or greater than 100 repeating units)and a high molecular weight (e.g. greater than or equal to 50,000 Da).Polymers are commonly the polymerization product of one or more monomerprecursors. The term polymer includes homopolymers, or polymersconsisting essentially of a single repeating monomer subunit. The termpolymer also includes copolymers which are formed when two or moredifferent types of monomers are linked in the same polymer. Copolymersmay comprise two or more monomer subunits, and include random, block,alternating, segmented, grafted, tapered and other copolymers.

An “oligomer” refers to a molecule composed of repeating structuralunits connected by covalent chemical bonds often characterized by anumber of repeating units less than that of a polymer (e.g., equal to orless than 10 repeating units) and a lower molecular weights (e.g. lessthan or equal to 50,000 Da) than polymers. Oligomers may be thepolymerization product of one or more monomer precursors. In anembodiment, an oligomer or a monomer cannot be considered a polymer inits own right.

A “prepolymer” refers to a polymer or oligomer the molecules of whichare capable of entering, through reactive groups, into furtherpolymerization. Routes to forming polyurethane polymers includepolymerization of diol and diisocyanate monomers and polymerization ofprepolymers including urethane linkages. In embodiments, thepolyurethane prepolymer is oligomeric. In father embodiments, thepolyurethane prepolymers include acrylate or methacrylate endgroups.

Oligomers and polymer mixtures can be characterized and differentiatedfrom other mixtures of oligomers and polymers by measurements ofmolecular weight and molecular weight distributions. The followingdefinitions of molecular weight can be applied for such characterization(see: L. H. Sperling, Introduction to Physical Polymer Science, 2^(nd)Ed., Wiley New York (1992).) The average Molecular Weight (M) is theAverage Number of Repeating Units n (or dp.)×the molecular weight ormolar mass (Mi) of the repeating unit. The number-average molecularweight (M_(n)) is the arithmetic mean, representing the total weight ofthe molecules present divided by the total number of molecules.Molecular weight may also be measured by the weight-average molecularweight (Mw) and the z-average molecular weight Mz,

In embodiments, one or more monomers or oligomers in the lightpolymerizable liquid composition contains one or more vinyl functionalgroups, which contain one or more carbon-carbon double bonds. The vinylfunctional groups in the system may be provided by, for example, allylethers, vinyl ethers, norbornenes, acrylates, methacrylates, acrylamidesor other monomers containing vinyl groups. In embodiments, the vinylmonomer or oligomer has at least one vinyl functional group, at leasttwo vinyl functional groups, at least three vinyl functional groups orat least four vinyl functional groups or from 2 to 4 thiol functionalgroups. In some embodiments, the vinyl monomer or oligomer may furthercomprise a hydroxyl group. In other embodiments, the vinyl monomer oroligomer does not comprise a hydroxyl group.

In embodiments, one of the monomers or oligomers in the lightpolymerizable liquid composition includes a thiol monomer or oligomer.As used herein, a thiol monomer or oligomer containing one or more thiolfunctional groups, which terminate with —SH. Monomers or oligomerscontaining thiol functional groups may be combined with monomers oroligomers comprising at least one aliphatic carbon-carbon double bond orat least one aliphatic carbon-carbon triple bond. In embodiments, thethiol monomer or oligomer has at least two thiol functional groups, atleast three thiol functional groups or at least four thiol functionalgroups or from 2 to 4 thiol functional groups. In different embodiments,a thiol-ene system has about 1-90% of its functional groups as thiolfunctional groups or 2%-65% thiol functional groups. The balance of thefunctional groups (35% to 98%) of the functional groups may be vinylfunctional groups.

In embodiments, the light polymerizable composition further includes afiller material. Soluble filler materials include, but are not limitedto poly(vinyl alcohol), poly(vinyl butyral-co-vinyl alcohol-co-vinylacetate), polycaprolactone, poly (methyl methacrylate),polycaprolactone-block-polytetrahydrofuran block-polycaprolactone,poly(vinyl chloride) or cellulose acetate butyrate, which may be used totune the viscosity. Inorganic fillers include, but are not limited tohydroxyapatite, fumed silica, colloidal silica, glass powders andβ-tricalciumphosphate, which may be used to improve the mechanicalproperties of the polymer.

Photoinitiators that are useful in the invention include those that canbe activated with light and initiate polymerization of the polymerizablecomponents of the formulation. In embodiments, the photoinitiator is aradical photoinitiator or a cationic initiator. In a further embodiment,the photoinitiator is a Type I photoinitiator which undergoes aunimolecular bond cleavage to generate free radicals. In an additionalembodiment the photoinitiator is a Type II photoinitiator whichundergoes a bimolecular reaction to generate free radicals. Common TypeI photoinitiators include, but are not limited to benzoin ethers, benzilketals, α-dialkoxy-acetophenones, α-hydroxy-alkyl phenones andacyl-phosphine oxides. Common Type II photoinitiators includebenzophenones/amines and thioxanthones/amines. Cationic initiatorsinclude aryldiazonium, diaryliodonium, and triarylsulfonium salts.

Photopolymerization occurs when suitable formulations are exposed tolight of sufficient power and of a wavelength capable of initiatingpolymerization. The wavelengths and power of light useful to initiatepolymerization depends on the initiator used. Light as used hereinincludes any wavelength and power capable of initiating polymerization.Preferred wavelengths of light include ultraviolet (UV) or visible. UVlight sources include UVA (wavelength about 400 nm to about 320 nm), UVB(about 320 nm to about 290 nm) or UVC (about 290 nm to about 100 nm).Any suitable source may be used, including laser sources. The source maybe broadband or narrowband, or a combination. The light source mayprovide continuous or pulsed light during the process. Both the lengthof time the system is exposed to UV light and the intensity of the UVlight can be varied to determine the ideal reaction conditions.

Additive manufacturing includes a variety of technologies whichfabricate three-dimensional objects directly from digital models throughan additive process. In some aspects, successive layers of material aredeposited and “cured in place.” A variety of techniques are known to theart for additive manufacturing, including selective laser sintering(SLS), fused deposition modeling (FDM) and jetting or extrusion. In manyembodiments, selective laser sintering involves using a laser beam toselectively melt and fuse a layer of powdered material according to adesired cross-sectional shape in order to build up the object geometry.In many embodiments, fused deposition modeling involves melting andselectively depositing a thin filament of thermoplastic polymer in alayer-by-layer manner in order to form an object. In yet anotherexample, 3D printing can be used to fabricate the appliances herein. Inmany embodiments, 3D printing involves jetting or extruding one or morematerials onto a build surface in order to form successive layers of theobject geometry.

Photopolymers may be fabricated by “vat” processes in which light isused to selectively cure a vat or reservoir of the photopolymer. Eachlayer of photopolymer may be selectively exposed to light in a singleexposure or by scanning a beam of light across the layer. Specifictechniques include sterolithography (SLA), Digital Light Processing(DLP) and two photon-induced photopolymerization (TPIP).

Continuous direct fabrication methods for photopolymers have also beenreported. For example, a direct fabrication process can achievecontinuous build-up of an object geometry by continuous movement of thebuild platform (e.g., along the vertical or Z-direction) during theirradiation phase, such that the hardening depth of the irradiatedphotopolymer is controlled by the movement speed. Accordingly,continuous polymerization of material on the build surface can beachieved. Such methods are described in U.S. Pat. No. 7,892,474, thedisclosure of which is incorporated herein by reference in its entirety.In yet another example, a continuous direct fabrication method utilizesa “heliolithography” approach in which the liquid photopolymer is curedwith focused radiation while the build platform is continuously rotatedand raised. Accordingly, the object geometry can be continuously builtup along a spiral build path. Such methods are described in U.S. PatentPublication No. 2014/0265034, the disclosure of which is incorporatedherein by reference in its entirety. Continous liquid interfaceproduction of 3D objects has also been reported (J. Tumbleston et al.,Science, 2015, 347 (6228), pp 1349-1352) hereby incorporated byreference in its entirety for description of the process. Anotherexample of continuous direct fabrication method can involve extruding acomposite material composed of a curable liquid material surrounding asolid strand. The composite material can be extruded along a continuousthree-dimensional path in order to form the object. Such methods aredescribed in U.S. Patent Publication No. 2014/0061974, the disclosure ofwhich is incorporated herein by reference in its entirety.

“Biocompatible” refers to a material that does not elicit animmunological rejection or detrimental effect, referred herein as anadverse immune response, when it is disposed within an in-vivobiological environment. For example, in embodiments a biological markerindicative of an immune response changes less than 10%, or less than20%, or less than 25%, or less than 40%, or less than 50% from abaseline value when a human or animal is exposed to or in contact withthe biocompatible material. Alternatively, immune response may bedetermined histologically, wherein localized immune response is assessedby visually assessing markers, including immune cells or markers thatare involved in the immune response pathway, in and adjacent to thematerial. In an aspect, a biocompatible material or device does notobservably change immune response as determined histologically. In someembodiments, the invention provides biocompatible devices configured forlong-term use, such as on the order of weeks to months, without invokingan adverse immune response. Biological effects may be initiallyevaluated by measurement of cytotoxicity, sensitization, irritation andintracutaneous reactivity, acute systemic toxicity, pyrogenicity,subacute/subchronic toxicity and/or implantation. Biological tests forsupplemental evaluation include testing for chronic toxicity.

“Bioinert” refers to a material that does not elicit an immune responsefrom a human or animal when it is disposed within an in-vivo biologicalenvironment. For example, a biological marker indicative of an immuneresponse remains substantially constant (plus or minus 5% of a baselinevalue) when a human or animal is exposed to or in contact with thebioinert material. In some embodiments, the invention provides bioinertdevices.

In embodiments, the crosslinked polymers are characterized by a tensilestress-strain curve that displays a yield point after which the testspecimen continues to elongate, but there is no increase in load. Suchyield point behavior typically occurs “near” the glass transitiontemperature, where the material is between the glassy and rubberyregimes and may be characterized as having viscoelastic behavior. Inembodiments, viscoelastic behavior is observed in the temperature range20° C. to 40° C. The yield stress is determined at the yield point. Insome embodiments, the yield point follows an elastic region in which theslope of the stress-strain curve is constant or nearly constant. Inembodiments, the modulus is determined from the initial slope of thestress-strain curve or as the secant modulus at 1% strain (e.g. whenthere is no linear portion of the stress-strain curve). The elongationat yield is determined from the strain at the yield point. When theyield point occurs at a maximum in the stress, the ultimate tensilestrength is less than the yield strength. For a tensile test specimen,the strain is defined by In (I/I₀), which may be approximated by(I−I₀)/I₀ at small strains (e.g. less than approximately 10%) and theelongation is I/I₀, where I is the gauge length after some deformationhas occurred and lo is the initial gauge length. The mechanicalproperties can depend on the temperature at which they are measured. Thetest temperature may be below the expected use temperature for a dentalappliance such as 35° C. to 40° C., In embodiments, the test temperatureis 23±2° C.

In embodiments, the stress relaxation can be measured by monitoring thetime-dependent stress resulting from a steady strain. The extent ofstress relaxation can also depend on the temperature. In embodiments,the test temperature is 37±2° C.

The dynamic viscosity of a fluid indicates its resistance to shearingflows. The SI unit for dynamic viscosity is the Poiseuille (Pa·s).Dynamic viscosity is commonly given in units of centipoise, where 1centipoise (cP) is equivalent to 1 mPa·s. Kinematic viscosity is theratio of the dynamic viscosity to the density of the fluid; the SI unitis m²/s. Devices for measuring viscosity include viscometers andrheometers.

Examples of devices that may be made by direct fabrication include, butare not limited to, those described in the following U.S. ProvisionalApplications filed Jul. 7, 2015: “MULTI-MATERIAL ALIGNERS”, U.S. Ser.No. 62/189,259; “DIRECT FABRICATION OF ALIGNERS WITH INTERPROXIMAL FORCECOUPLING”, U.S. Ser. No. 62/189,263; “DIRECT FABRICATION OF ORTHODONTICAPPLIANCES WITH VARIABLE PROPERTIES”, U.S. Ser. No. 62/189,291; “DIRECTFABRICATION OF ALIGNERS FOR ARCH EXPANSION”, U.S. Ser. No. 62/189,271;“DIRECT FABRICATION OF ATTACHMENT TEMPLATES WITH ADHESIVE”, U.S. Ser.No. 62/189,282; “DIRECT FABRICATION CROSS-LINKING FOR PALATE EXPANSIONAND OTHER APPLICATIONS”, U.S. Ser. No. 62/189,301; “SYSTEMS, APPARATUSESAND METHODS FOR DENTAL APPLIANCES WITH INTEGRALLY FORMED FEATURES”, U.S.Ser. No. 62/189,312; “DIRECT FABRICATION OF POWER ARMS”, U.S. Ser. No.62/189,317; “SYSTEMS, APPARATUSES AND METHODS FOR DRUG DELIVERY FROMDENTAL APPLIANCES WITH INTEGRALLY FORMED RESERVOIRS”, U.S. Ser. No.62/189,303 and “DENTAL APPLIANCE HAVING ORNAMENTAL DESIGN”, U.S. Ser.No. 62/189,318, each of which is hereby incorporated by reference in itsentirety.

STATEMENTS REGARDING INCORPORATION BY REFERENCE AND VARIATIONS

All references cited throughout this application, for example patentdocuments including issued or granted patents or equivalents; patentapplication publications; and non-patent literature documents or othersource material; are hereby incorporated by reference herein in theirentireties, as though individually incorporated by reference, to theextent each reference is at least partially not inconsistent with thedisclosure in this application (for example, a reference that ispartially inconsistent is incorporated by reference except for thepartially inconsistent portion of the reference).

The terms and expressions which have been employed herein are used asterms of description and not of limitation, and there is no intention inthe use of such terms and expressions of excluding any equivalents ofthe features shown and described or portions thereof, but it isrecognized that various modifications are possible within the scope ofthe invention claimed. Thus, it should be understood that although thepresent invention has been specifically disclosed by preferredembodiments, exemplary embodiments and optional features, modificationand variation of the concepts herein disclosed may be resorted to bythose skilled in the art, and that such modifications and variations areconsidered to be within the scope of this invention as defined by theappended claims. The specific embodiments provided herein are examplesof useful embodiments of the present invention and it will be apparentto one skilled in the art that the present invention may be carried outusing a large number of variations of the devices, device components,methods steps set forth in the present description. As will be obviousto one of skill in the art, methods and devices useful for the presentmethods can include a large number of optional composition andprocessing elements and steps.

When a group of substituents is disclosed herein, it is understood thatall individual members of that group and all subgroups, including anyisomers, enantiomers, and diastereomers of the group members, aredisclosed separately. When a Markush group or other grouping is usedherein, all individual members of the group and all combinations andsubcombinations possible of the group are intended to be individuallyincluded in the disclosure. When a compound is described herein suchthat a particular isomer, enantiomer or diastereomer of the compound isnot specified, for example, in a formula or in a chemical name, thatdescription is intended to include each isomers and enantiomer of thecompound described individual or in any combination. Additionally,unless otherwise specified, all isotopic variants of compounds disclosedherein are intended to be encompassed by the disclosure. For example, itwill be understood that any one or more hydrogens in a moleculedisclosed can be replaced with deuterium or tritium. Isotopic variantsof a molecule are generally useful as standards in assays for themolecule and in chemical and biological research related to the moleculeor its use. Methods for making such isotopic variants are known in theart. Specific names of compounds are intended to be exemplary, as it isknown that one of ordinary skill in the art can name the same compoundsdifferently.

It must be noted that as used herein and in the appended claims, thesingular forms “a”, “an”, and “the” include plural reference unless thecontext clearly dictates otherwise. Thus, for example, reference to “acell” includes a plurality of such cells and equivalents thereof knownto those skilled in the art, and so forth. As well, the terms “a” (or“an”), “one or more” and “at least one” can be used interchangeablyherein. It is also to be noted that the terms “comprising”, “including”,and “having” can be used interchangeably. The expression “of any ofclaims XX-YY” (wherein XX and YY refer to claim numbers) is intended toprovide a multiple dependent claim in the alternative form, and in someembodiments is interchangeable with the expression “as in any one ofclaims XX-YY.”

Unless defined otherwise, all technical and scientific terms used hereinhave the same meanings as commonly understood by one of ordinary skillin the art to which this invention belongs. Although any methods andmaterials similar or equivalent to those described herein can be used inthe practice or testing of the present invention, the preferred methodsand materials are now described. Nothing herein is to be construed as anadmission that the invention is not entitled to antedate such disclosureby virtue of prior invention.

Every formulation or combination of components described or exemplifiedherein can be used to practice the invention, unless otherwise stated.

Whenever a range is given in the specification, for example, atemperature range, a time range, or a composition or concentrationrange, all intermediate ranges and subranges, as well as all individualvalues included in the ranges given are intended to be included in thedisclosure. As used herein, ranges specifically include the valuesprovided as endpoint values of the range. For example, a range of 1 to100 specifically includes the end point values of 1 and 100. It will beunderstood that any subranges or individual values in a range orsubrange that are included in the description herein can be excludedfrom the claims herein.

As used herein, “comprising” is synonymous with “including,”“containing,” or “characterized by,” and is inclusive or open-ended anddoes not exclude additional, unrecited elements or method steps. As usedherein, “consisting of” excludes any element, step, or ingredient notspecified in the claim element. As used herein, “consisting essentiallyof” does not exclude materials or steps that do not materially affectthe basic and novel characteristics of the claim. In each instanceherein any of the terms “comprising”, “consisting essentially of” and“consisting of” may be replaced with either of the other two terms. Theinvention illustratively described herein suitably may be practiced inthe absence of any element or elements, limitation or limitations whichis not specifically disclosed herein.

One of ordinary skill in the art will appreciate that startingmaterials, biological materials, reagents, synthetic methods,purification methods, analytical methods, assay methods, and biologicalmethods other than those specifically exemplified can be employed in thepractice of the invention without resort to undue experimentation. Allart-known functional equivalents, of any such materials and methods areintended to be included in this invention. The terms and expressionswhich have been employed are used as terms of description and not oflimitation, and there is no intention that in the use of such terms andexpressions of excluding any equivalents of the features shown anddescribed or portions thereof, but it is recognized that variousmodifications are possible within the scope of the invention claimed.Thus, it should be understood that although the present invention hasbeen specifically disclosed by preferred embodiments and optionalfeatures, modification and variation of the concepts herein disclosedmay be resorted to by those skilled in the art, and that suchmodifications and variations are considered to be within the scope ofthis invention as defined by the appended claims.

STATEMENTS REGARDING CHEMICAL COMPOUNDS AND NOMENCLATURE

As used herein, the term “group” may refer to a functional group of achemical compound. Groups of the present compounds refer to an atom or acollection of atoms that are a part of the compound. Groups of thepresent invention may be attached to other atoms of the compound via oneor more covalent bonds. Groups may also be characterized with respect totheir valence state. The present invention includes groups characterizedas monovalent, divalent, trivalent, etc. valence states.

As used herein, the term “substituted” refers to a compound wherein ahydrogen is replaced by another functional group.

Alkyl groups include straight-chain, branched and cyclic alkyl groups.Alkyl groups include those having from 1 to 30 carbon atoms. Alkylgroups include small alkyl groups having 1 to 3 carbon atoms. Alkylgroups include medium length alkyl groups having from 4-10 carbon atoms.Alkyl groups include long alkyl groups having more than 10 carbon atoms,particularly those having 10-30 carbon atoms. The term cycloalkylspecifically refers to an alky group having a ring structure such asring structure comprising 3-30 carbon atoms, optionally 3-20 carbonatoms and optionally 3-10 carbon atoms, including an alkyl group havingone or more rings. Cycloalkyl groups include those having a 3-, 4-, 5-,6-, 7-, 8-, 9- or 10-member carbon ring(s) and particularly those havinga 3-, 4-, 5-, 6-, 7- or 8-member ring(s). The carbon rings in cycloalkylgroups can also carry alkyl groups. Cycloalkyl groups can includebicyclic and tricycloalkyl groups. Alkyl groups are optionallysubstituted. Substituted alkyl groups include among others those whichare substituted with aryl groups, which in turn can be optionallysubstituted. Specific alkyl groups include methyl, ethyl, n-propyl,iso-propyl, cyclopropyl, n-butyl, s-butyl, t-butyl, cyclobutyl,n-pentyl, branched-pentyl, cyclopentyl, n-hexyl, branched hexyl, andcyclohexyl groups, all of which are optionally substituted. Substitutedalkyl groups include fully halogenated or semihalogenated alkyl groups,such as alkyl groups having one or more hydrogens replaced with one ormore fluorine atoms, chlorine atoms, bromine atoms and/or iodine atoms.Substituted alkyl groups include fully fluorinated or semifluorinatedalkyl groups, such as alkyl groups having one or more hydrogens replacedwith one or more fluorine atoms. An alkoxy group is an alkyl group thathas been modified by linkage to oxygen and can be represented by theformula R—O and can also be referred to as an alkyl ether group.Examples of alkoxy groups include, but are not limited to, methoxy,ethoxy, propoxy, butoxy and heptoxy. Alkoxy groups include substitutedalkoxy groups wherein the alky portion of the groups is substituted asprovided herein in connection with the description of alkyl groups. Asused herein MeO— refers to CH₃O—.

Alkenyl groups include straight-chain, branched and cyclic alkenylgroups. Alkenyl groups include those having 1, 2 or more double bondsand those in which two or more of the double bonds are conjugated doublebonds. Alkenyl groups include those having from 2 to 20 carbon atoms.Alkenyl groups include small alkenyl groups having 2 to 3 carbon atoms.Alkenyl groups include medium length alkenyl groups having from 4-10carbon atoms. Alkenyl groups include long alkenyl groups having morethan 10 carbon atoms, particularly those having 10-20 carbon atoms.Cycloalkenyl groups include those in which a double bond is in the ringor in an alkenyl group attached to a ring. The term cycloalkenylspecifically refers to an alkenyl group having a ring structure,including an alkenyl group having a 3-, 4-, 5-, 6-, 7-, 8-, 9- or10-member carbon ring(s) and particularly those having a 3-, 4-, 5-, 6-,7- or 8-member ring(s). The carbon rings in cycloalkenyl groups can alsocarry alkyl groups. Cycloalkenyl groups can include bicyclic andtricyclic alkenyl groups. Alkenyl groups are optionally substituted.Substituted alkenyl groups include among others those that aresubstituted with alkyl or aryl groups, which groups in turn can beoptionally substituted. Specific alkenyl groups include ethenyl,prop-1-enyl, prop-2-enyl, cycloprop-1-enyl, but-1-enyl, but-2-enyl,cyclobut-1-enyl, cyclobut-2-enyl, pent-1-enyl, pent-2-enyl, branchedpentenyl, cyclopent-1-enyl, hex-1-enyl, branched hexenyl, cyclohexenyl,all of which are optionally substituted. Substituted alkenyl groupsinclude fully halogenated or semihalogenated alkenyl groups, such asalkenyl groups having one or more hydrogens replaced with one or morefluorine atoms, chlorine atoms, bromine atoms and/or iodine atoms.Substituted alkenyl groups include fully fluorinated or semifluorinatedalkenyl groups, such as alkenyl groups having one or more hydrogen atomsreplaced with one or more fluorine atoms.

Aryl groups include groups having one or more 5-, 6-, 7- or 8-memberaromatic rings, including heterocyclic aromatic rings. The termheteroaryl specifically refers to aryl groups having at least one 5-,6-, 7- or 8-member heterocyclic aromatic rings. Aryl groups can containone or more fused aromatic rings, including one or more fusedheteroaromatic rings, and/or a combination of one or more aromatic ringsand one or more nonaromatic rings that may be fused or linked viacovalent bonds. Heterocyclic aromatic rings can include one or more N,O, or S atoms in the ring. Heterocyclic aromatic rings can include thosewith one, two or three N atoms, those with one or two O atoms, and thosewith one or two S atoms, or combinations of one or two or three N, O orS atoms. Aryl groups are optionally substituted. Substituted aryl groupsinclude among others those that are substituted with alkyl or alkenylgroups, which groups in turn can be optionally substituted. Specificaryl groups include phenyl, biphenyl groups, pyrrolidinyl,imidazolidinyl, tetrahydrofuryl, tetrahydrothienyl, furyl, thienyl,pyridyl, quinolyl, isoquinolyl, pyridazinyl, pyrazinyl, indolyl,imidazolyl, oxazolyl, thiazolyl, pyrazolyl, pyridinyl, benzoxadiazolyl,benzothiadiazolyl, and naphthyl groups, all of which are optionallysubstituted. Substituted aryl groups include fully halogenated orsemihalogenated aryl groups, such as aryl groups having one or morehydrogens replaced with one or more fluorine atoms, chlorine atoms,bromine atoms and/or iodine atoms. Substituted aryl groups include fullyfluorinated or semifluorinated aryl groups, such as aryl groups havingone or more hydrogens replaced with one or more fluorine atoms. Arylgroups include, but are not limited to, aromatic group-containing orheterocylic aromatic group-containing groups corresponding to any one ofthe following: benzene, naphthalene, naphthoquinone, diphenylmethane,fluorene, anthracene, anthraquinone, phenanthrene, tetracene,tetracenedione, pyridine, quinoline, isoquinoline, indoles, isoindole,pyrrole, imidazole, oxazole, thiazole, pyrazole, pyrazine, pyrimidine,purine, benzimidazole, furans, benzofuran, dibenzofuran, carbazole,acridine, acridone, phenanthridine, thiophene, benzothiophene,dibenzothiophene, xanthene, xanthone, flavone, coumarin, azulene oranthracycline. As used herein, a group corresponding to the groupslisted above expressly includes an aromatic or heterocyclic aromaticgroup, including monovalent, divalent and polyvalent groups, of thearomatic and heterocyclic aromatic groups listed herein provided in acovalently bonded configuration in the compounds of the invention at anysuitable point of attachment. In embodiments, aryl groups containbetween 5 and 30 carbon atoms. In embodiments, aryl groups contain onearomatic or heteroaromatic six-member ring and one or more additionalfive- or six-member aromatic or heteroaromatic ring. In embodiments,aryl groups contain between five and eighteen carbon atoms in the rings.Aryl groups optionally have one or more aromatic rings or heterocyclicaromatic rings having one or more electron donating groups, electronwithdrawing groups and/or targeting ligands provided as substituents.

Arylalkyl groups are alkyl groups substituted with one or more arylgroups wherein the alkyl groups optionally carry additional substituentsand the aryl groups are optionally substituted. Specific alkylarylgroups are phenyl-substituted alkyl groups, e.g., phenylmethyl groups.Alkylaryl groups are alternatively described as aryl groups substitutedwith one or more alkyl groups wherein the alkyl groups optionally carryadditional substituents and the aryl groups are optionally substituted.Specific alkylaryl groups are alkyl-substituted phenyl groups such asmethylphenyl. Substituted arylalkyl groups include fully halogenated orsemihalogenated arylalkyl groups, such as arylalkyl groups having one ormore alkyl and/or aryl groups having one or more hydrogens replaced withone or more fluorine atoms, chlorine atoms, bromine atoms and/or iodineatoms.

As used herein, the terms “alkylene” and “alkylene group” are usedsynonymously and refer to a divalent group derived from an alkyl groupas defined herein. The invention includes compounds having one or morealkylene groups. Alkylene groups in some compounds function as attachingand/or spacer groups. Compounds of the invention may have substitutedand/or unsubstituted C₁-C₂₀ alkylene, C₁-C₁₀ alkylene and C₁-C₅ alkylenegroups.

As used herein, the terms “cycloalkylene” and “cycloalkylene group” areused synonymously and refer to a divalent group derived from acycloalkyl group as defined herein. The invention includes compoundshaving one or more cycloalkylene groups. Cycloalkyl groups in somecompounds function as attaching and/or spacer groups. Compounds of theinvention may have substituted and/or unsubstituted C₃-C₂₀cycloalkylene, C₃-C₁₀ cycloalkylene and C₃-C₅ cycloalkylene groups.

As used herein, the terms “arylene” and “arylene group” are usedsynonymously and refer to a divalent group derived from an aryl group asdefined herein. The invention includes compounds having one or morearylene groups. In some embodiments, an arylene is a divalent groupderived from an aryl group by removal of hydrogen atoms from twointra-ring carbon atoms of an aromatic ring of the aryl group. Arylenegroups in some compounds function as attaching and/or spacer groups.Arylene groups in some compounds function as chromophore, fluorophore,aromatic antenna, dye and/or imaging groups. Compounds of the inventioninclude substituted and/or unsubstituted C₃-C₃₀ arylene, C₃-C₂₀ arylene,C₃-C₁₀ arylene and C₁-C₅ arylene groups.

As used herein, the terms “heteroarylene” and “heteroarylene group” areused synonymously and refer to a divalent group derived from aheteroaryl group as defined herein. The invention includes compoundshaving one or more heteroarylene groups. In some embodiments, aheteroarylene is a divalent group derived from a heteroaryl group byremoval of hydrogen atoms from two intra-ring carbon atoms or intra-ringnitrogen atoms of a heteroaromatic or aromatic ring of the heteroarylgroup. Heteroarylene groups in some compounds function as attachingand/or spacer groups. Heteroarylene groups in some compounds function aschromophore, aromatic antenna, fluorophore, dye and/or imaging groups.Compounds of the invention include substituted and/or unsubstitutedC₃-C₃₀ heteroarylene, C₃-C₂₀ heteroarylene, C₁-C₁₀ heteroarylene andC₃-C₅ heteroarylene groups.

As used herein, the terms “alkenylene” and “alkenylene group” are usedsynonymously and refer to a divalent group derived from an alkenyl groupas defined herein. The invention includes compounds having one or morealkenylene groups. Alkenylene groups in some compounds function asattaching and/or spacer groups. Compounds of the invention includesubstituted and/or unsubstituted C₂-C₂₀ alkenylene, C₂-C₁₀ alkenyleneand C₂-C₅ alkenylene groups.

As used herein, the terms “cylcoalkenylene” and “cylcoalkenylene group”are used synonymously and refer to a divalent group derived from acylcoalkenyl group as defined herein. The invention includes compoundshaving one or more cylcoalkenylene groups. Cycloalkenylene groups insome compounds function as attaching and/or spacer groups. Compounds ofthe invention include substituted and/or unsubstituted C₃-C₂₀cylcoalkenylene, C₃-C₁₀ cylcoalkenylene and C₃-C₅ cylcoalkenylenegroups.

As used herein, the terms “alkynylene” and “alkynylene group” are usedsynonymously and refer to a divalent group derived from an alkynyl groupas defined herein. The invention includes compounds having one or morealkynylene groups. Alkynylene groups in some compounds function asattaching and/or spacer groups. Compounds of the invention includesubstituted and/or unsubstituted C₂-C₂₀ alkynylene, C₂-C₁₀ alkynyleneand C₂-C₅ alkynylene groups.

As used herein, the term “halo” refers to a halogen group such as afluoro (—F), chloro (—Cl), bromo (—Br) or iodo (—I)

The term “heterocyclic” refers to ring structures containing at leastone other kind of atom, in addition to carbon, in the ring. Examples ofsuch heteroatoms include nitrogen, oxygen and sulfur. Heterocyclic ringsinclude heterocyclic alicyclic rings and heterocyclic aromatic rings.Examples of heterocyclic rings include, but are not limited to,pyrrolidinyl, piperidyl, imidazolidinyl, tetrahydrofuryl,tetrahydrothienyl, furyl, thienyl, pyridyl, quinolyl, isoquinolyl,pyridazinyl, pyrazinyl, indolyl, imidazolyl, oxazolyl, thiazolyl,pyrazolyl, pyridinyl, benzoxadiazolyl, benzothiadiazolyl, triazolyl andtetrazolyl groups. Atoms of heterocyclic rings can be bonded to a widerange of other atoms and functional groups, for example, provided assubstituents.

The term “carbocyclic” refers to ring structures containing only carbonatoms in the ring. Carbon atoms of carbocyclic rings can be bonded to awide range of other atoms and functional groups, for example, providedas substituents.

The term “alicyclic ring” refers to a ring, or plurality of fused rings,that is not an aromatic ring. Alicyclic rings include both carbocyclicand heterocyclic rings.

The term “aromatic ring” refers to a ring, or a plurality of fusedrings, that includes at least one aromatic ring group. The term aromaticring includes aromatic rings comprising carbon, hydrogen andheteroatoms. Aromatic ring includes carbocyclic and heterocyclicaromatic rings. Aromatic rings are components of aryl groups.

The term “fused ring” or “fused ring structure” refers to a plurality ofalicyclic and/or aromatic rings provided in a fused ring configuration,such as fused rings that share at least two intra ring carbon atomsand/or heteroatoms.

As used herein, the term “alkoxyalkyl” refers to a substituent of theformula alkyl-O-alkyl.

As used herein, the term “polyhydroxyalkyl” refers to a substituenthaving from 2 to 12 carbon atoms and from 2 to 5 hydroxyl groups, suchas the 2,3-dihydroxypropyl, 2,3,4-trihydroxybutyl or2,3,4,5-tetrahydroxypentyl residue.

As used herein, the term “polyalkoxyalkyl” refers to a substituent ofthe formula alkyl-(alkoxy)n-alkoxy wherein n is an integer from 1 to 10,preferably 1 to 4, and more preferably for some embodiments 1 to 3.

As to any of the groups described herein that contain one or moresubstituents, it is understood that such groups do not contain anysubstitution or substitution patterns which are sterically impracticaland/or synthetically non-feasible. In addition, the compounds of thisinvention include all stereochemical isomers arising from thesubstitution of these compounds. Optional substitution of alkyl groupsincludes substitution with one or more alkenyl groups, aryl groups orboth, wherein the alkenyl groups or aryl groups are optionallysubstituted. Optional substitution of alkenyl groups includessubstitution with one or more alkyl groups, aryl groups, or both,wherein the alkyl groups or aryl groups are optionally substituted.Optional substitution of aryl groups includes substitution of the arylring with one or more alkyl groups, alkenyl groups, or both, wherein thealkyl groups or alkenyl groups are optionally substituted.

Optional substituents for any alkyl, alkenyl and aryl group includessubstitution with one or more of the following substituents, amongothers:

halogen, including fluorine, chlorine, bromine or iodine;

pseudohalides, including —CN, —OCN (cyanate), —NCO (isocyanate), —SCN(thiocyanate) and —NCS (isothiocyanate);

—COOR, where R is a hydrogen or an alkyl group or an aryl group and morespecifically where R is a methyl, ethyl, propyl, butyl, or phenyl groupall of which groups are optionally substituted;

—COR, where R is a hydrogen or an alkyl group or an aryl group and morespecifically where R is a methyl, ethyl, propyl, butyl, or phenyl groupall of which groups are optionally substituted;

—CON(R)₂, where each R, independently of each other R, is a hydrogen oran alkyl group or an aryl group and more specifically where R is amethyl, ethyl, propyl, butyl, or phenyl group all of which groups areoptionally substituted; and where R and R can form a ring which cancontain one or more double bonds and can contain one or more additionalcarbon atoms;

—OCON(R)₂, where each R, independently of each other R, is a hydrogen oran alkyl group or an aryl group and more specifically where R is amethyl, ethyl, propyl, butyl, or phenyl group all of which groups areoptionally substituted; and where R and R can form a ring which cancontain one or more double bonds and can contain one or more additionalcarbon atoms;

—N(R)₂, where each R, independently of each other R, is a hydrogen, oran alkyl group, or an acyl group or an aryl group and more specificallywhere R is a methyl, ethyl, propyl, butyl, phenyl or acetyl group, allof which are optionally substituted; and where R and R can form a ringthat can contain one or more double bonds and can contain one or moreadditional carbon atoms;

—SR, where R is hydrogen or an alkyl group or an aryl group and morespecifically where R is hydrogen, methyl, ethyl, propyl, butyl, or aphenyl group, which are optionally substituted;

—SO₂R, or —SOR, where R is an alkyl group or an aryl group and morespecifically where R is a methyl, ethyl, propyl, butyl, or phenyl group,all of which are optionally substituted;

—OCOOR, where R is an alkyl group or an aryl group;

—SO₂N(R)₂, where each R, independently of each other R, is a hydrogen,or an alkyl group, or an aryl group all of which are optionallysubstituted and wherein R and R can form a ring that can contain one ormore double bonds and can contain one or more additional carbon atoms;

—OR, where R is H, an alkyl group, an aryl group, or an acyl group allof which are optionally substituted. In a particular example R can be anacyl yielding —OCOR″, wherein R″ is a hydrogen or an alkyl group or anaryl group and more specifically where R″ is methyl, ethyl, propyl,butyl, or phenyl groups all of which groups are optionally substituted.

Specific substituted alkyl groups include haloalkyl groups, particularlytrihalomethyl groups and specifically trifluoromethyl groups. Specificsubstituted aryl groups include mono-, di-, tri, tetra- andpentahalo-substituted phenyl groups; mono-, di-, tri-, tetra-, penta-,hexa-, and hepta-halo-substituted naphthalene groups; 3- or4-halo-substituted phenyl groups, 3- or 4-alkyl-substituted phenylgroups, 3- or 4-alkoxy-substituted phenyl groups, 3- or4-RCO-substituted phenyl, 5- or 6-halo-substituted naphthalene groups.More specifically, substituted aryl groups include acetylphenyl groups,particularly 4-acetylphenyl groups; fluorophenyl groups, particularly3-fluorophenyl and 4-fluorophenyl groups; chlorophenyl groups,particularly 3-chlorophenyl and 4-chlorophenyl groups; methylphenylgroups, particularly 4-methylphenyl groups; and methoxyphenyl groups,particularly 4-methoxyphenyl groups.

As to any of the above groups that contain one or more substituents, itis understood that such groups do not contain any substitution orsubstitution patterns which are sterically impractical and/orsynthetically non-feasible. In addition, the compounds of this inventioninclude all stereochemical isomers arising from the substitution ofthese compounds.

The invention may be further understood by the following non-limitingexamples.

EXAMPLE 1 Properties for Selected Formulations and Testing Methods

Table 1 gives exemplary formulations which were measured as having amodulus in the range 800 MPa to 2000 MPa, a tensile strength of 20 MPato 55 mPa, an elongation at yield greater than 4% and a elongation@breakgreater than 40% (composition ratios by weight):

TABLE 1 Formulation Composition Exo10/CEA/NVP 30/50/20Exo10/PETMP:TATATO 30/70 (2:1.1) Exo10/CEA/NVP 20/70/10 CN3211/CEA/NVP20/60/20

Table 2 gives exemplary formulations which were measured as having amodulus in the range 800 MPa to 2000 MPa, a tensile strength of 20 MPato 55 mPa, an elongation at yield greater than 4% and a elongation@breakfrom 30% to 40% (composition ratios by weight):

TABLE 2 Formulation Composition Exo108/NVP/CEA 33/33/33Exo108/CEA/SR833S 30/50/20 CN991/NVP/CEA 20/40/40 CN991/NVP/CN978230/60/10 Exo108/IBOA/NVP 20/20/60 CN3211/CEA/IPDI-UDMA 20/60/20CN3211/CEA/SR833S 20/60/20

Protocols

The mixing protocol was as follows. All of the formulations were mixedwith a Flacktek Speedmixer™ (1.5 minutes at 2700 rpm) and contained 0.5wt % TPO-L as the photoinitiator.

The curing protocol was as follows. The samples were cured into dog bonemolds, 1 mm thickness, 6 mm width and 12 or 35 mm length. Samples werecured with a 395 nm LED light at an intensity of 10 mW/cm² for 45seconds or with a 385 nm Heraeus NobleCure light at an intensity of 80mW/cm² for 15 seconds.

The tensile properties protocol was as follows. Tensile properties weremeasured with a TestResources Materials Testing System. The crossheadspeed was 2.5 mm/min. The dog bones were 35 mm long for assessment ofmechanical properties for Tables 1 and 2.

TABLE 3 Acrylate Monomers and Oligomers Product Code ChemicalName/Classification Viscosity (cP) SR 833S Tricyclodecane dimethanoldiacrylate   130 @ 25 C. SR 368D Tris (2-hydroxy ethyl) isocyanurate  330 @ 25 C. triacrylate SR 368 Tris (2-hydroxy ethyl) isocyanuratetriacrylate CN 991 Aliphatic urethane diacrylate oligomer   600 @ 60 C.CN 9782 Aromatic urethane diacrylate oligomer  42000 @ 60 C. CN 3211Aliphatic urethane acrylate oligomer  27500 @ 25 C. CN 9009 Urethaneacrylate PU 3201NT Aliphatic trifunctional methacrylate  15,000 @ 25 C.PE210 Bisphenol A Epoxy Acrylate   5,000 @ 60 C. TPGDA Tripropyleneglycol diacrylate   15-20 @ 25 C. PU340 Aliphatic trifunctional acrylate 70,000 @ 25 C. ME 2110 Modified epoxy acrylate   4,000 @ 65 C. Exo10Dimethacrylate urethane 816000 @ 25 C. Exo 108 Dimethacrylate urethane176000 @ 25 C. IPDI-UDMA Isophorone Urethane Dimethacrylate UDMAUrethane dimethacrylate

TABLE 4 Additional Monomers Product Code Chemical Name/ClassificationViscosity (cP) IBOA Isobornyl acrylate  7 @ 25 C. IBOMA IsobornylMethacrylate M1130 Trimethyl cyclohexyl acrylate 1-10 @ 25 C.   M151Tetrahydrofurfuryl methacrylate 10 @ 25 C. NVP 1-vinyl-2-pyrrolidinone 2 @ 20 C. SR833S Tricyclodecane dimethanol diacrylate 130 @ 25 C. TATATO 1,3,5-Triallyl-1,3,5-triazine- 2,4,6(1H,3H,5H)-trione PETMPPentaerythritol tetrakis(3-mercaptopropionate) CEAβ-carboxyethylacrylate 73 @ 25 C.

EXAMPLE 2 3D Printing

For 3D printing, samples were formulated with 0.1 or 0.08 wt % UVblocker (OB+, Mayzo, Suwanee, Ga.) and 2 or 0.5 wt % photoinitiator. AnAuto Desk Ember 3D printer (DLP SLA) was utilized with a 405 nm LEDprojector and build plate with dimensions of 64 mm by 40 mm. The layerthickness was 25 μm and the exposure time was 4 seconds/layer. Afterprinting, the parts were rinsed with methanol and post cured with the385 nm Heraeus NobleCure light for 30 minutes.

We claim:
 1. A crosslinked polymer for use in an orthodontic appliance,the crosslinked polymer comprising: a first repeating unit derived froma urethane (meth)acrylate oligomer; a second repeating unit derived froma vinyl or thiol monomer; and a tensile modulus from 800 MPa to 2000MPa, a tensile strength at yield of 20 MPa to 55 MPa, an elongation atyield greater than 4% and an elongation at break greater than 30%. 2.The crosslinked polymer of claim 1, wherein at least one of the urethane(meth)acrylate oligomer, the vinyl monomer and the thiol monomercomprises at least two polymerizable groups.
 3. The crosslinked polymerof claim 2, wherein the amount of the first repeating unit is from 25 to50 wt % and the amount of the second repeating unit is from 50 to 75 wt%, with the total amount of the first repeating unit and the secondrepeating unit being greater than or equal to 70 wt %.
 4. Thecrosslinked polymer of claim 1, wherein the crosslinked polymer furthercomprises a third repeating unit derived from a second urethane(meth)acrylate oligomer or a second vinyl or thiol monomer not includinga urethane linkage, wherein at least one of the urethane (meth)acrylateoligomer(s) and the vinyl or thiol monomer(s) comprises at least twopolymerizable groups.
 5. The crosslinked polymer of claim 4, wherein theamount of the first repeating unit is from 15 to 40 wt %, the amount ofthe second repeating unit is from 15 to 75 wt % and the amount of thethird repeating unit is from 2 to 60 wt %, with the total amount of thefirst repeating unit, the second repeating unit and the third repeatingunit being greater than or equal to 70 wt %.
 6. The crosslinked polymerof claim 4, wherein the second repeating unit is derived from a vinylmonomer not including a urethane linkage.
 7. The crosslinked polymer ofclaim 4, wherein the second repeating unit is derived from1-vinyl-2-pyrrolidinone (NVP), β-carboxyethylacrylate-(CEA), trimethylcyclohexyl acrylate (TMCHA), tetrahydrofurfuryl methacrylate (THFMA),isobornyl acrylate (IBOA), or isobornyl methacrylate (IBOMA).
 8. Thecrosslinked polymer of claim 1, wherein the urethane (meth)acrylateoligomer is selected from the group consisting of a urethanedimethacrylate oligomer, an isophorone urethane dimethacrylate oligomer,a urethane diacrylate oligomer, and a urethane triacrylate oligomer. 9.The crosslinked polymer of claim 1, wherein the second repeating unit isderived from an acrylate monomer.
 10. The crosslinked polymer of claim1, wherein the crosslinked polymer has a transmittance equal to orgreater than 80% for light having a wavelength in the visible region.11. The crosslinked polymer of claim 1, wherein the crosslinked polymercomprises a plurality of polymer layers.
 12. The crosslinked polymer ofclaim 1, wherein the crosslinked polymer is transparent, translucent, oropaque.
 13. The crosslinked polymer of claim 4, wherein the thirdrepeating unit is derived from a urethane (meth)acrylate oligomer orvinyl monomer not including a urethane linkage.
 14. The crosslinkedpolymer of claim 4, wherein the third repeating unit is derived from athiol monomer.